In various multistage turbomachines used for energy conversion, such as gas turbines, a fluid is used to produce rotational motion. Referring to FIG. 1, an axial flow gas turbine 10 includes a multi-stage compressor section 12, a combustion section 14, a multi stage turbine section 16 and an exhaust system 18 arranged along a center axis 20. Air at atmospheric pressure is drawn into the compressor section 12 generally in the direction of the flow arrows F along the axial length of the turbine 10. The intake air is progressively compressed in the compressor section 12 by rows of rotating compressor blades, thereby increasing pressure, and directed by mating compressor vanes to the combustion section 14, where it is mixed with fuel, such as natural gas, and ignited to create a combustion gas. The combustion gas, which is under greater pressure, temperature and velocity than the original intake air, is directed to the turbine section 16. The turbine section 16 includes a plurality of airfoil shaped turbine blades 22 arranged in a plurality of rows R1, R2, etc. on a shaft 24 that rotates about the axis 20. The combustion gas expands through the turbine section 16 where it is directed in a combustion flow direction F across the rows of blades 22 by associated rows of stationary vanes 24. A row of blades 22 and associated row of vanes 24 form a stage. In particular, the turbine section 16 may include four stages. As the combustion gas passes through the turbine section 16, the combustion gas causes the blades 22 and thus the shaft to rotate about the axis 20, thereby extracting energy from the flow to produce mechanical work.
The combustion section 14 includes several individual combustion assemblies 26 each including a basket and nozzle and arranged in a circular array about the axis 20. A respective circular array of transition ducts, also known as transition pieces 28, connects the outflow of each combustor assembly 26 to an inlet of the turbine section 16. Each transition piece 28 may be a tubular or other appropriately shaped structure that channels the combustion gas between a combustion chamber and a first row or stage of stationary vanes of the turbine section 16.
A downstream end 30 of each transition piece 28 includes an exit frame 32 that is attached to a corresponding inlet of the turbine section 16 thus forming a circular array of adjacent exit frames about the axis 20. Radially outer and inner seals are used on each exit frame 32 to seal against respective radially outer and inner retainer elements of a turbine inlet to minimize air leakage between the transition piece 28 and the turbine inlet. Further, side seals are used between adjacent exit frames 32 to minimize air leakage between the exit frames 32. It is desirable to enhance the longevity and reliability of the sealing arrangement between the exit frames 32 and the side seals in order to maintain engine efficiency and performance while also reducing repair costs.